
function is_valid_email_address($email){
		$qtext = '[^\\x0d\\x22\\x5c\\x80-\\xff]';
		$dtext = '[^\\x0d\\x5b-\\x5d\\x80-\\xff]';
		$atom = '[^\\x00-\\x20\\x22\\x28\\x29\\x2c\\x2e\\x3a-\\x3c'.
			'\\x3e\\x40\\x5b-\\x5d\\x7f-\\xff]+';
		$quoted_pair = '\\x5c[\\x00-\\x7f]';
		$domain_literal = "\\x5b($dtext|$quoted_pair)*\\x5d";
		$quoted_string = "\\x22($qtext|$quoted_pair)*\\x22";
		$domain_ref = $atom;
		$sub_domain = "($domain_ref|$domain_literal)";
		$word = "($atom|$quoted_string)";
		$domain = "$sub_domain(\\x2e$sub_domain)*";
		$local_part = "$word(\\x2e$word)*";
		$addr_spec = "$local_part\\x40$domain";
		return preg_match("!^$addr_spec$!", $email) ? 1 : 0;
}

if (is_valid_email_address('cal@example.com')) {
   print 'cal@example.com is a valid e-mail address';
} else {
   print 'cal@example.com is not a valid e-mail address';
}
